Apparatus for coupling logging cable to borehole tool

ABSTRACT

Apparatus is provided for coupling a logging cable to a borehole tool. The logging cable is coupled to a cable head which in turn is connected to the borehole tool by way of a hollow, cylindrical mandrel and a concentrically mounted, freely rotatable ring. One end of the mandrel is threaded into the cable head. The other end of the mandrel is inserted into a receptacle in one end of the borehole tool, and the ring is threaded to that end to couple the cable to the borehole tool.

Elite States Patent [191 Straus [451 Sept. 25, 1973 APPARATUS FORCOUPLING LOGGING CABLE TO BOREHOLE TOOL [75] Inventor: Andrew J. D.Straus, Dallas, Tex.

[73] Assignee: Mobil Oil Corporation, New York,

22 Filed: Oct. 18,1971

211 Appl, No.: 190,027

[52] US. Cl. 339/28, 285/356 1 Int. Cl H0lr 13/54 Field of Search339/28, 89, 177, 339/26; 285/356, 357, 18

[56] References Cited UNITED STATES PATENTS 2,326,037 8/1943 Jung285/356 X 2,481,404 9/1949 Donner 285/356 X 3,530,423 9/1970 Davis339/89 C 3,054,848 9/1962 Reesby et a1... 339/177 R X 2,367,175 1/1945Hahn 339/89 R X Primary ExaminerMarvin A. Champion AssistantExaminerTerrell P. Lewis AttorneyWilliam J. Scherback et al.

[5 7] ABSTRACT Apparatus is provided for coupling a logging cable to aborehole tool. The logging cable is coupled to a cable head which inturn is connected to the borehole tool by way of a hollow, cylindricalmandrel and a concentrically mounted, freely rotatable ring. One end ofthe mandrel is threaded into the cable head. The other end of themandrel is inserted into a receptacle in one end of the borehole tool,and the ring is threaded to that end to couple the cable to the boreholetool.

2 Claims, 4 Drawing Figures Patented Sept. 25, 1973 3,761,863

2 Sheets-Sheet 1 PRIOR ART BOREHOLE COARSE FINE CABLE TOOL. THREADSTHREADS HEAD \COUPLING RING FIG.I

ANDREW J. D. STRAUS INVENTOR Patented Sept. 25,1973 7 3,761,863

2 Sheets-Sheet 2 FIG. 28

3I\ t as -30 I v 34\ I 44 H1 39K? :1 J

ANDREW J. D. STRA US INVENTOR APPARATUS FOR COUPLING LOGGING CABLE TOBOREIIOLE TOOL BACKGROUND OF THE INVENTION This invention relates towell logging and more particularly to apparatus for coupling a loggingcable to a borehole tool.

Well logging tools are used extensively in determining various physicalproperties of subterranean strata penetrated by a borehole. Suchproperties are determined by lowering a well logging tool, capable ofmaking the desired determination, into the well borehole to the desiredstrata. The well logging tools are commonly electrically operated andcontain sensitive elements which are responsive to the physicalproperties of the subterranean strata. By measurement or recordation ofthe response of the sensitive element, information as to the physicalproperties of the subterranean strata is obtained.

A suitable coupling must be provided for electrically connecting thesensitive element of the borehole tool to the logging cable leading toinstrumentation on the surface of the earth. It has been the generalpractice to couple a borehole tool having coarse, external threads alongone end to a cable head having fine, external threads along one end bymeans of a coupling ring, such ring being internally threaded forengagement with both the borehole tool and the cable head. The

pitch of the threads on the borehole tool are different from that of thecable head. That is, for a borehole tool with coarse threads, the cablehead will have fine threads. An illustration of this type coupling isset forth in FIG. 1 of the accompanying drawings to assist in anunderstanding of the prior art. To effect such. coupling, the ring isthreadably engaged with the first few threads of both the borehole tooland the cable head. Rotation of the ring simultaneously advances theborehole tool and the cable head. As a consequence ofthe difference inthreading pitch, the borehole tool will be advanced more rapidly by therotation of the ring than will the cable head, thereby effecting a tightfit.

Considerable rotational force is required to effect a tight connectioneven to the extent that wrenches or hand tools may be needed. Anotherproblem is that well liquids and foreign particles commonly get into thethreads of the borehole tool, the cable head, and the coupling ring,thereby requiring the threads to be cleaned prior to each coupling ofthe cable head to a borehole tool.

SUMMARY OF THE INVENTION When several logging operations are to beperformed utilizing different size and type logging tools, theforegoing-described problems can make the logging operation quitetime-consuming and therefore costly to the total logging operation.

The present invention is directed'to a coupler, for quickly and easilyconnecting and disconnecting a logging cable to a borehole tool, whichcomprises a hollow, cylindrical mandrel and a rotatable ring adapted tobe slidably mounted on the mandrel for rotation about and translationalong the length of the mandrel.

The ring is reduced and threaded at one end. The mandrel is providedwith external threads along one end of its outer wall and formsahexagonal configuration at the other end. The mandrel has a peripheralflange adjacent the hexagonal end. Translational movement of the ringalong the mandrel results in a thrust of the ring against the peripheralflange, such thrust advancing the mandrel into the borehole tool.

In assembling the cable head, the threaded end of the ring is mountedover the threaded end of the mandrel. The threaded end of the mandrel isthen fitted into a cable head housing in which the logging cable isterminated. A tight fit is effected between the mandrel and cable headby applying torque to the hexagonal end of the sleeve.

In coupling the cable head to the borehole tool, the hexagonal end ofthe mandrel is inserted into an internally threaded extension of theborehole tool. The ring is then rotated and threadably advanced into theextension, such advancement resulting in a thrust against the flange ofthe mandrel, thereby advancing the mandrel into the extension tocomplete the assembly.

The mandrel is circumferentially grooved in the outer wall adjacent itsthreaded end and also in the peripheral flange adjacent the hexagonalend to retain 0- rings. Upon completing the coupling of the mandrel toboth the cable head and the borehole tool extension, the entire chamberleading from the logging cable in the cable head through the mandrel andthe extension into the borehole tool is sealed by the O-rings fromborehole liquids and particles.

I BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a welllogging tool coupler representative of the prior art.

FIGS. 2A and 2B are sectional views of, the well logging tool couplerconstructed in accordance with the present invention. I

FIG. 3 is an end view of a portion of the well logging coupler of FIGS.2A and 28 viewed along the line A-A of FIG. 2A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 2A and28, a borehole tool 10 is coupled to a logging cable by a couplercomprised generally of mandrel 11 and a rotatable ring 12.

The borehole tool 10 has a hollow, cylindrical, inner cavity 13 forhousing the sensitive logging elements. The too] 10 is affixedlyattached to one end of a hollow, cylindrical tool extension 14 by capscrews 15. The other end of said tool extension 14 is bored to provide ashoulder 16. The end portion of the recessed inner wall has threads 17.

Mandrel 11 is generally a hollow cylinder with one end of the outer wallmachined to form a hexagonal outer surface 41, as can be seen withreference to FIG. 3. The mandrel is machined adjacent the hexagonal endto'provide flanges l8 dimensioned to be inserted into tool extension 14.The flanges l8'are separated by circumferential grooves 19 retainingO-rings 20 for sealing the inner chamber of the coupler from boreholeliquids and particles. Affixed to the end of-mandrel 11 by means ofscrews 22 is a connector 23 with feed through terminals 230. Connector23 is flanged at its receptacle face 23b to provide a surface forabuttedly mating against the shoulder 16 of tool extension 14.

The opposite end of mandrel 11 is provided with external threads 24. Theoutside wall of mandrel 11 immediately adjacent the threads 24 includesa circumferential groove 25 retaining O-ring 26 for sealing the loggingtool from borehole liquids and particles.

Rotatable ring 12 has an internal diameter dimensioned to providemounting over mandrel 11. The outside wall of ring 12 is recessed toprovide for a shoulder 29. The recessed outer wall is threaded alongmuch of its length with the same gauge threads as threads 17 of toolextension 14 and has a circumferential groove 27 located adjacent theshoulder 29 for retaining O-ring 28 which engages tool extension 14. Theinner surface of ring 12 has two circumferential grooves 42 and 44 forretaining O-rings 43 and 45 which engage mandrel 11. Engagement of ring12 with 'tool extension 14 causes ring 12 to be advanced into toolextension 14, with the resulting thrust of the ring 12 against flange 18advancing mandrel 11 to a point where the connector 23 engages shoulder16 of tool extension 14.

Cable head 21 is a hollow, cylindrical housing with internal threads atone end of the same gauge as threads 24 on mandrel 11. A shoulder 40limits the movement of mandrel 11. Cable head 21 is also internallythreaded at the opposite end with threads 30 to provide for connectionwith logging cable casing 31. Cable head 21 is bored and counterbored toprovide a shoulder 32.

A connector 34 is provided with a circumferential groove 35 retainingO-ring 36 for sealing the cable head 21 from borehole liquids andparticles. Connector 34 is held fixed with respect to cable head 21 byone end 33 of casing 31 which engages one side of the ter- I minal andforces the other side against shoulder 32. The casing 31 is a hollow,cylindrical casing externally threaded to connect with the threads ofcable head 21. A logging cable (not shown) will pass through the casing31 and connect with feed through terminals 34:: of connector 34.

As previously discussed, it is a specific feature of the presentinvention to provide a coupler which can be quickly and easilydisconnected. Nevertheless, there are provided spanner holes 39 in eachthe tool extension 14, the ring 12, the cable head 21, and the casing31. Such spanner holes are provided should it be found desirable or evennecessary under abnormal operating conditions, such as freezingtemperatures, to use greater torque in connecting and disconnecting thecoupler.

There has been shown in the preferred embodiment herein a tool extension14 connected to the borehole tool 10 by way of screws 15. However, itwould be possible to design a logging tool wherein the borehole tool andthe tool extension are integral.

Likewise, there has been shown in the preferred embodiment a cable head21 mated to a logging cable casing 31. Again, it would be possible todesign a logging tool wherein the cable head and the logging cablecasing are integral.

To connect the cable head 21 to the borehole tool 10, the ring 12 isfirst slipped over mandrel 1 l. A cable (not shown) is then electricallycoupled from terminals 23a of connector 23 through the chamber providedby mandrel 11 to terminals 34a of connector 34 in cable head 21. Mandrel11 is then threaded into cable head 21. Such threading is accomplishedby engaging a wrench or other suitable tool with the hexagonal end ofmandrel 11 and rotating the mandrel until it is in tight abutment fitwith shoulder 40 of cable head 21. An- 6 23a of connector 23. Mandrel 11is then inserted into too] extension 14 until the threads of ring 12 canbe engaged with the threads 17 of tool extension 14. Ring 12 is rotatedand threadably advanced into tool extension 14, thereby providing athrust against the flange 18 of mandrel 11 to advance mandrel l1 andconnector 23 to a point where connector 23 is abuttedly mated withshoulder 16 of tool extension 14. An easy connection of ring 12 withtool extension 14 is thereby effected since very little rotational forceis required to thread ring 12 into tool extension 14. It will be notedthat after ring 12 is completely engaged with tool extension 14 andconnector 23 is abuttedly mated with tool extension 14, there is a space34 between ring 12 and cable head 21 which allows ring 12 to be rotatedin reverse direction so as to disengage the coupling of mandrel 11 withtool extension 14.

It is another feature of the present invention to provide a couplerwhich is sealed from borehole liquids and particles under the boreholepressure of a logging operation, thereby allowing an operator todisconnect the mandrel from the borehole tool after a logging operationand to connect another borehole tool to the mandrel without having toclean borehole liquids and particles from in and around the mandrel.Such a sealing is provided by O-rings 20 retained in mandrel 11 andO-rings 28, 43, and 45 retained in ring 12. A further scaling isprovided for the cable head 21 by O-ring 26 retained in mandrel l1 andO-ring 36 retained in connector 34. Consequently, the entire chamber ofthe coupler from connector 34 through cable head 21, mandrel l1, andtool extension 14 to borehole tool 10 is sealed from borehole liquidsand particles and will remain at atmospheric pressure under which theassembly operation is carried out.

Various modifications to the disclosed embodiment as well as alternateembodiments may become apparent to one skilled in the art withoutdeparting from the scope and spirit of the invention as defined by theappending claims.

1 claim:

1. Well logging apparatus for connecting a logging cable to a boreholetool, comprising:

a. a hollow, cylindrical borehole tool having a closed end forcontaining the borehole instrumentation and an open end bored to providean internal shoulder, said open end being internally threaded along aportion of the bore immediately adjacent said open end,

b. a hollow, cylindrical cable head housing internally threaded alongone end and containing a first connector concentrically mounted therein,said logging cable being connected to said first connector,

c. a hollow, cylindrical mandrel with a peripheral flange adjacent oneend for insertion into said borehole tool and having the other endexternally threaded for engagement with the internal threading of saidcable head,

d. a second connector mounted concentrically within said mandrel andforming an integral part of the end of said mandrel which is adapted tobe slidably inserted into said borehole tool, and

e. a rotatable ring slidably mounted over the threaded end of saidmandrel and threadably engaged by external threading with the internalthreading of said borehole tool whereby, upon rotation, said ring isadvanced into said borehole tool 2. The coupler as set forth in claim 1wherein:

said mandrel further includes O-rings retained in circumferentialgrooves in said peripheral flange and immediately adjacent said threadedportion, thereby providing a seal at the surface interface points ofsaid mandrel with both said borehole tool and said cable head housingfor sealing the passageway from said cable head housing to said boreholetool.

1. Well logging apparatus for connecting a logging cable to a boreholetool, comprising: a. a hollow, cylindrical borehole tool having a closedend for containing the borehole instrumentation and an open end bored toprovide an internal shoulder, said open end being internally threadedalong a portion of the bore immediately adjacent said open end, b. ahollow, cylindrical cable head housing internally threaded along one endand containing a first connector concentrically mounted therein, saidlogging cable being connected to said first connector, c. a hollow,cylindrical mandrel with a peripheral flange adjacent one end forinsertion into said borehole tool and having the other end externallythreaded for engagement with the internal threading of said cable head,d. a second connector mounted concentrically within said mandrel andforming an integral part of the end of said mandrel which is adapted tobe slidably inserted into said borehole tool, and e. a rotatable ringslidably mounted over the threaded end of said mandrel and threadablyengaged by external threading with the internal threading of saidborehole tool whereby, upon rotation, said ring is advanced into saidborehole tool with the resulting thrust of said ring against saidperipheral flange of said mandrel advancing said mandrel into saidborehole tool and into an abutment mating with the internal shoulder ofsaid borehole tool, said logging cable being electrically coupled fromsaid first connector in said cable head housing through the passagewayprovided by said cable head housing and said mandrel to said secondconnector in said mandrel and from said second connector to the boreholeinstrumentation within said borehole tool.
 2. The coupler as set forthin claim 1 wherein: said mandrel further includes O-rings retained incircumferential grooves in said peripheral flange and immediatelyadjacent said threaded portion, thereby providing a seal at the surfaceinterface points of said mandrel with both said borehole tool and saidcable head housing for sealing the passageway from said cable headhousing to said borehole tool.